Gaseous electric discharge device



July 23, 1935. M. PIRANI ET AL 2,009,201

GASEOUS ELECTRIC DISCHARGE DEVICE Filed July 25, 1929 InvGhtOrs: MBT'OGHO Fir'an'u Kurt NLtschk e The'm Attohngy.

Patented July 23, 1935- PATENT OFFICE GASEOUS ELECTRIC DISCHARGE DEVICE Marcello 'Pirani and Kurt Nitschke, Berlin-Wilmersdort, Germany,

assignors to General Electric Company, a corporation of New York Application July 25, 1929, Serial No. 381,036

r In Germany August 1, 1928 2 Claims. (c1. 176-125) The present invention relates to gaseous electric discharge devices.

Heretotore, electric discharge tubes with a filling of common gases, such as carbonic acid gas, nitrogen, hydrogen, because of the quick clean up of such gases under a low pressure of gas filling, have been provided with a floating valve for automatically feeding needed gas replenishments into the tube. Such a floating valve in shipment of the tube is easily deranged and rendered ineffective, and, turther, much space is taken up by the gas generators such as the containers for the .hydrochloric acid and marble dust in the generation of .carbonic acid gas and the readily ignitable phosphorus used in the generation of nitrogen, and for these reasons, it has been proposed recently to mount such gas replenishing materials either in an offset of the discharge tube or in a ,hollow space in the electrodes 01 said discharge tube. Such materials are, for example, magnesium carbonate, sodium azide, lithium hydride, and these are heated by the operation of the tube itself. That is, when the current density exceeds a predetermined value the gas evolving material is heated, gas is evolved and the gas content of the tube is replenished. In these devices the gas evolving material is constantly subjected to heat radiated from the positive column of the discharge, or the radiations from the electrod or from a heater wire connected in series with the light tube circuit. In all these'methods, in spite of the most careful measuring of the quantity of the gas evolving material and the surfaces of the containing chamber, it sometimes happens that the gas pressure in the tube, in the course of time, mounts to a disadvantageous degree during the operation of the device.

The object this invention is to avoid the over-'- supply or gas into the electric discharge device. For this purpose, the gas producing material, during the operation of the device, is heated by an electric heating means (heater wire, heat mantel orv heat ring) automatically put in the circuit when the current density of the tube exceeds a predetermined value. The invention attains its object by maintaining the gas evolving material inactive under normal-operating conditions and instantly, as soon as the current density of the tube exceeds a predetermined value, the heating means starts the gas evolution. For the purpose of putting the heating means into the circuit when the tube current density becomes high an electromagnet connected to one of the current leads of the electric discharge device is used. The core of said electro-magnet acts as the circuit closing device of,the heater circuit and is connected to the primary or secondary of the tube transformer.

By the use of the above described new method and apparatus only a very short heating of the gas evolving material takes place with a conse- 5 quent quick evolution of gas. This is advantageous in practice, as the gas evolving material need not, unless desired, be placed in the interior of the tube, likewise .there is no necessity for a heating container in which is placed in pulverized form the gas evolving material as said material may now be used in the shape of a rod heated by a surrounding or imbedded heating wire filament or else a. heat mantel. The said rod is made by suitably pressing pulverized gas evolving material and then sintering it. Many of the pulverized gas feeders, for example magnesium carbonate, are, however, in large part decom-- posed during the sintering operation and hence such rods prepared by the old methods give oil? little or no gas in the operation of the tube. 1 have discovered that this condition is remedied when the rod shaped body comprises a mixture of pulverized gas evolving material and a material having a lower sintering point than the gas evolving material, for example, pulverized glass or enamel and used as a sintered binding material. After the mixture has been pressed into .shape it is sintered at the lower sintering temperature of the binding material. In this sintering process the pulverized, contained particles of the gas emitting material are not used up as has been the case heretofore.

In Figs. 1 and 2 of the drawing are shown two circuits for the new light tube, and Fig. 3 shows an alternative embodiment with the gas evolving material contained in an offset chamber.

The light tube as shown in Fig. 1 consists oi. a cylindrical chamber l of any desired glass or 40 else of a glass which permits the passage of ultra-violet rays, and at each of its ends are mounted inner electrodes 2, or outer electrodes may be used. The tube l can be filled exclusively with a common gas, for example, carbonic acid gas, nitrogen, or hydrogen or else also with a mixture of suitable common gases with a rare gas or gases, for example neon, helium, argon, crypton, xenon. Both the electrodes 2 are connected by leads 3 to the secondaryiwinding 4 of a transformer, the primargwinding 5 or which is connected with a s table current supply through a resistance 6. v

In series in one of the current leads 3 of the tube I is an electro-magnet I, the core 8 of which I tion sure of the gas contacts I 0, I0. To these contacts are connected leads II, II which are connected to a wire I2, made of high melting" point metal such as chrome nickel, platin etc., sealed into a small offset chamber I3 of the tube I, to heat rod I4. The latter together with the heating wire I2 can be sealed into the interior of the light tube I or else as shown, into a very small chamber I3 of the light tube. The rod I4 consists of a mixture of a gas evolving material and a material which can be sintered at a lower temperature than the decomposition temperature of the gas emitting material. As the gas evolving substance for supplying the light tube with carbonic acid gas, nitrogen, or hydrogen, I use, magnesium carbonate, calcium carbonate, sodium or barium azide, sodium or barium nitride or lithium hydride; Pulverized glass or pulverized enamel can be used material for said gas evolving compounds. In the manufacture of the gas evolving rods the pulverized materials after thorough mixing are pressed into rod. shape and heated up to the sintering point of the binding material. The pulverized particles of the gas evolving material thus become attached to each other without change of physical or chemical condition. By sintering the rods it is possible to drive oil? a part of the occluded gases in the rod with safety,

and to prevent the remainder from entering intogas forming contamination in the rod, the sintering and the subsequent cooling taking place in a container which is either evacuated or else in which a continuous stream of the samegas is maintained as that which is given oif by the gas evolving material in the rod when the rod is heated to a'higher temperature.

Withcommon gases present in the tube I, at normal pressure and with normal current flowing through the tube, current does not pass through heater I2, as the core 8 is not raised. Therefore, under normal starting conditions the 4 contacts III are bridged by conducting plate 9 of the electromagnet core 8 and theheater circuit starts only between electrodes 2. During operaof the tube I, should the gas pressure go down to a predetermined point and the current density of the tube rise correspondingly, the core ofthe electro-magnet I, 8, is drawn up with a consequent raising of the plate 9 from the con- .tacts a consequence, the rod I4 is heated and now filling of the tube and the current through the tube have reached normal operating conditions. 1

reached the core 8 instantly falls again to its nected in series with the I connected across "rest position on the contacts I0, lllcutting out the heater.

While in-the circuit control shown in Fig. 1 the heater circuit is connected to the secondary winding of the transformers, it is possible to connect the heater circuit as in Fig. 2 to'the primary winding of the transformers. In this case also the winding I of an electro-magnet 'I, 8 is conlead 3 of the light tube; and the core 8 carries a current conducting'piate 9. In this case, however, the contacts II are leads I5, I5 of the transformer primary by leads I6, l6. Inv this embodiment,

he contacts are the electrodes 2 of the tube under normal so ditions. The rising of the current density in the as the lowtemperature sintering bindingis short circuited and the current discharge I0. Current then flows through the heater wire I2, and, as

gives oil gas, until the pres- As soon as these conditions are open and current flows only to 2,009,201- carriesa conducting plate 9, which bridges the tube again causes the actuation of the core I of the electro-magnet bridges the contacts III, which closes the heater circuit I2, I6, which then operates in the same manner as the circuit described in Fig. '1.

To produce a slow and gradual diffusion of the replenishing gas which starts immediately upon the closing of the heater circuit'of the gas evolving material, a tube I8 can, as shown in Fig. 3, be sealed in the connecting part I1 between the light tube I and the off-set chamber I3 which contains the .gas evolving rod I4. The tube I 8 is'open only toward the interior of the light tube I and, therefore, acts as a dividing body between light tube I, and offset chamber I3. This tube I8 is surrounded by winding I9 in series with the heater wire I2 and is heated therefore simultaneously with the rod I 4, when the gas pressure in the tube drops andcauses the current density of the tube to exceed a. predetermined value. The tube I8 consists of a material, such, for example, as palladium, which is permeable to the evolved nitrogen andhydrogen gas only when heated. As the diffusion takes. place over a long period, by regulating the electro -magnet I, 8, and the heating means of the rod I4, it is possible to cause the evolved feeding gas to seep slowly into the light tube. In this case the normal gas pressure in the tube I also is controlling and as soon as the normal gas pressure is again established the heater wire I2 and the heater wire I9 are both out out of circuit whereby the large current to the gas feeding ,devices is interrupted and an oversupply of replenishing gas into the light tube is thus avoided.

The new heating means for a gas feeding ma- I,8sothattheplate!" terial need not necessarily entirely supply the gas from the material coftained in the main electrode, whilejthe prod ction of the correct working proportion, the lacking part of the feeding gases, is supplied bythe heated gas emitting ma;- terial By the utilization of this new heating means, the whole gas feeding is so exact that an oversupplyv of gas in'the tube as well as the productionof an undesired higher pressure is avoided. Then too the gas producing main electrodes can now be sodesigned, in contrast to the former prac-' tice, that they continually and indeed even with unfavorable working I conditions, for example, overloading, give ofl a Sligh ly smaller quantity of replenishing than is needed. Therefore, the auxiliary apparatus, consisting of the heating means I, I, II, in connection with the gas evolving material I4, and dividing tube II, through which the replenishing gas slowly difluses' into the lamp tube, can be ofrelatively small dimensions be-,, cause of the provision of the gas evolving main electrodes in the electric discharge device itself. Such electrodes, by giving off most of the replenishing gas needed by the device in operation, save the auxiliary apparatus from frequentuse, which lessens the wear and tearon said gas replenishing apparatus, and lengthens the life of the lamp tube as a whole,'resulting in a compact and rugged unit and a practically steady and uniform operation of said gaseous-electric discharge device for a practically indefinite life. The dividing body I! of palladium-in the connecting part II between the light tube l and the offset chamber I! can, if desired, be made in other shapes, and in other ways be mounted in the connecting part. Inoperation when the dividingbody is heated it is pervious to the feeder gas and it is not material, whether the gas evolving substance as shown be used in the shape or solid rods or loose powder or even also slabs. Furthermore, the dividing body and the gas evolving material can be heated by a single heater such as the heater wire It.

"What we claim as new and desire to secure by Letters Patent 0! the United States, is

1. In an electric discharge device, a container, electrodes for said container, a gas filling in said container, a gas supply chamber for said con- 'when heated, and means tainer, a gas evolving material in said chamber, a dividing body between said container and said chamber pervious to the evolved gas only when heated, and means controlled by current flowing in said container for heating said gas evolving material and said dividing body.

.2. In an electric discharge devi a container, gas evolving electrodes for said container, a gas filling in said container, 9. gas supply chamber for said container, a gas evolving material in said chamber, a dividing body between said container and said chamber pervious to the evolved gas only controlled by current flowing in said container for heating said gas evolving material and said dividing body. 

